Display assemblies of electronic display devices that provide indicia using display elements such as liquid crystals are known. For example, indicia are provided in a conventional liquid crystal display (LCD) assembly by selectively actuating liquid crystals to control passage of light. Such a conventional LCD assembly includes transparent media, such as glass or plastics, to sandwich one or more layers of such liquid crystals.
Light required to form the indicia with liquid crystals has to pass through the liquid crystals to a viewer. Such light is typically provided with either a light source or ambient light. The light source can placed to the rear of an LCD assembly so that the light generated can pass through the liquid crystals of the LCD assembly to the viewer. Such a light source provides what is commonly referred to as backlighting. Alternatively, the light source can be placed in front of the liquid crystals. Placed as such to provide frontlighting, which is similar to how ambient light is provided, the light that is generated has to pass through the liquid crystals to be reflected back to the viewer. With frontlighting or ambient light, the LCD assembly requires a reflector, placed on the other side of the liquid crystals relative to the light source, to reflect the light back to the viewer.
Viewing from both sides of an LCD assembly is desirable in applications such as, for example, a portable electronic device that is folded to reduce its size when not in use. For such applications, being viewable from an opposite side enables a user to preview indicia without having to unfold the portable electronic device. However, a problem with viewing a conventional LCD assembly from opposite sides is that the LCD assembly must then permit passage of light through both opposite sides and, as such, external background not related to the indicia on one side can then be seen from an opposite side. Such background is undesirable because it tends to interfere with viewing from the opposite side. Conventional reflectors to block the external background on one side does not overcome this problem as these will also block incident light required to view indicia from that one side.
To overcome the above problem, U.S. Pat. No. 5,115,228 describes electronic shutters of liquid crystal emulsion flashing rapidly to enable viewing of information from opposite surfaces of a display. However, such electronic shutters require complex driving circuitry to control timing of the flashing and to process the information. Providing two separate LCD assemblies may solve the problem but substantially increases the cost of the assembly and, furthermore, additional space is required which is undesirable for use in, for example, portable electronic devices. Hence, a need exists for a single display assembly to provide indicia that are viewable from opposite sides without requiring relatively complex driving circuitry or additional costs.